Apr 15, 20233 min read

Prepare in a Year - Tsunamis

The Pacific Coast, Strait of Juan de Fuca, Puget Sound, and large lakes are at risk from tsunamis, which are a series of extremely long waves that threaten people and property along shorelines. Sudden raising or lowering of the earth’s crust during earthquakes are usually the main cause of a tsunami, although landslides and underwater volcanic eruptions also can generate them.

The most frequent cause of Puget Sound tsunamis is landslides. The 1949 Olympia earthquake triggered a landslide in the Tacoma Narrows that caused a 6 to 8-foot tsunami that affected nearby shorelines three days after the earthquake.

Natural Warning Signs

There may not always be enough time for an official warning, so it is important that you understand natural warning signs. If you are at the shore and you…

• feel a strong or long earthquake • see a sudden rise or fall of the ocean, or • hear a loud roar from the ocean

…a tsunami may follow very soon. This is your warning! Take action immediately and move to a safe place (to high ground or inland) immediately. Do not wait to receive an official alert or instructions.

Tsunami messages are issued by the Tsunami Warning Centers to notify emergency managers and other local officials, the public, and other partners about the potential for a tsunami following a possible tsunami-generating event. These are not alerts that require a subscription to receive.

· Tsunami Warning: Take Action—Danger! A tsunami that may cause widespread flooding is expected or occurring. Dangerous coastal flooding and powerful currents are possible and may continue for several hours or days after initial arrival. Follow instructions from local officials. Evacuation is recommended. Move to high ground or inland (away from the water).

· Tsunami Advisory: Take Action—A tsunami with potential for strong currents or waves dangerous to those in or very near the water is expected or occurring. There may be flooding of beach and harbor areas. Stay out of the water and away from beaches and waterways. Follow instructions from local officials.

· Tsunami Watch: Be Aware—A distant earthquake has occurred. A tsunami is possible. Stay tuned for more information. Be prepared to take action if necessary.

· Tsunami Information Statement: No Action Needed—An earthquake has occurred, but there is no threat or it was very far away and the threat has not been determined. In most cases, there is no threat of a destructive tsunami.

Evacuation Assembly Sites

The site should be: 1) Outside the tsunami hazard area. 2) Easy to get to. 3) Capable of accommodating a large number of people. 4) Not blocking roadways – leaving access for emergency vehicles. 5) Assembly areas must be on publicly-owned property – If it is on private property, you will need the permission of the owner.

Practice walking your chosen evacuation route, even in darkness and bad weather. This will make evacuation quicker and easier during an emergency.

Be Prepared The time between waves ranges from five minutes to two hours. The first wave may not be the largest or the most damaging. Dangerous coastal flooding and powerful currents may last for several hours or days.

• LEARN what the hazards are, what areas are at risk

• KNOW the natural warning signs/alerting mechanisms

• Have a plan ready BEFORE the event happens • TRAIN on the plan

• WORK with others in your port/business areas